The present invention relates to an immobilization agent for industrial waste effective for making harmless industrial waste containing toxic heavy metals.
Conventionally, when industrial waste containing toxic heavy metals were treated, a procedure in which hydraulic cement and the waste was mixed in a weight ratio of 1:1 and water was added and milled together and then cured and solidified to immobilize the toxic heavy metals has been used. At least 150 kg of cement was used for 1 m.sup.3 of the waste in the waste treatment in 1977. However, such a treating method by using normal portland cement has various problems and is liable to cause secondary pollution unless the uses are limited.
For example, in the treatment of collected toxic dust exhausted from the workshop such as an electric furnace of steel plant, when a conventional treatment for making the dust harmless (immobilization) is carried out by using cement alone, the toxic metals contained in the collected dust are made lower than the regulated level according to the official leach out inspecting method ( Notification No. 13 of the Environment Agency of Japan) and solidified and capsuled except lead (Pb). At present, however, lead cannot be fixed to the regulated leaching level even if the treating condition such as the amount of cement added is varied and a treatment such as an use in landfilling (reclamation) cannot be carried out.
In the case of sludge containing highly concentrated copper (Cu) and nickel (Ni) discharged from the water-treating equipment of a semiconductor plant is treated by a conventional treating method with cement and determined by the leaching test method adopted by the State of California, U.S., these metals cannot be fixed to the regulated leaching level in U.S. and, at present, secondary pollution problems after the treatment due to the use in landfilling with incomplete treatment has occurred.
Thus, nowadays, regardless of domestic or abroad, it becomes seriously necessary to immobilize the industrial waste containing toxic heavy metals. An immobilization agent for industrial waste which can solidify and capsule (enclose) surely the solidified toxic heavy metals even when used in landfilling or dump to the sea and leaches no toxic heavy metals again and causes no secondary pollution has been required.
The object of the present invention is to provide an immobilization agent for industrial waste which can solve the above-mentioned problems of conventional technologies and can immobilize and capsule surely the industrial waste containing various toxic heavy metals and can make them stable compounds with no second leach out.